Why silica works well in tyres

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The softer the rubber in a tyre, the better the grip;this much is clear. But things get a little more complicated when you factor in silica, make from hard sand, that actually hardens a tyre. Normally this would reduce friction and thus grip. But while silica is harder and tougher than the carbon black it replaces, it has one big advantage. The silica grains exposed at the tread's contact patch are harder to break than carbon black grains. This makes them protrude from the surface even more, making the wear surface on a silica tyre rougher than that of a carbon black-only tyre. And that means better grip, especially in the wet. Also since this enables the use of a somewhat harder ribber , tyre deformation and resulting rolling resistance are less too.And so is fuel consumption and tyre wear. But it costs more.